1. Field of the Invention
The present invention relates to a novel ink (a recording liquid) which hardly clogs an orifice of a recording head even when the head is left unused for a long time, and which, when used for recording on an uncoated paper sheet, such as, an ordinary type of paper widely used in offices, schools and the like, achieves a high-density recorded image, exhibits printing characteristics substantially stable regardless of the type of recording paper, and achieves red, green and blue mono-color printing with high consistency and reproducibility. The present invention further relates to an ink jet recording method using the ink and recording unit and apparatus using the ink.
2. Description of the Related Art
There have been proposed a wide variety of ink compositions for recording on recording media, for example, ink compositions for writing utensils, stamps, various recording meters and ink jet recording apparatus. These compositions are aqueous or organic solutions or dispersions of dyes.
Further, various ink jet recording methods have been proposed. In one method, electrically charged ink droplets are continuously produced, some of which are used for recording. In another method, a signal is inputted to a recording head having a piezoelectric element, and an ink droplet is produced in response to the signal. In still another method, thermal energy corresponding to a recording signal is applied to the ink contained in a chamber of a recording head, thereby producing an ink droplet.
Compared with inks for writing utensils, stamps and recording meters, the inks for such ink jet recording methods must achieve superior characteristics compatible with the features of the ink jet recording methods. For example, they must have very good ejection characteristics, such as low orifice-clogging characteristic, quick responsiveness to signals, and high suitability for high-speed recording, and very good recording characteristics, such as low bleeding characteristic, and high density printing.
Various yellow inks, magenta inks and cyan inks have been developed, and some of those inks have already been used for full-color recording.
However, red, green and blue inks highly suitable for ink jet recording have not been developed. Such inks would be useful particularly for a so-called mono-color recording method. By the mono-color recording method, printing can be made in a desired color simply by setting a cartridge containing an ink of the desired color in a recording apparatus, if such an ink is available. Such mono-color recording is increasingly needed for the purpose of, for example, printing business documents or personal post cards. In short, the need for red, green and blue inks highly suitable for ink jet recording are growing.